There is nothing quite like a large-scale extinction event to clear out the competitors, provide room for new ecological niches, and speed up development for those species that are fortunate enough to survive. Is that not the case? According to the findings of a recent research, the pace of climatic change may have an equally important role in the acceleration of evolutionary processes.
The research focuses on the development of reptiles over a period of 57 million years, beginning before the great extinction that occurred at the end of the Permian Period and continuing far beyond it. Around 252 million years ago, heightened volcanic activity on Earth was the cause of an extinction catastrophe that wiped out an astounding 86 percent of the planet’s species. Carbon dioxide was released into the atmosphere and seas as a result of this increased activity. Despite this, reptiles have made a respectable recovery from the upheaval. It is generally accepted that they slithered their way into newly accessible niches at that period, which led to an explosion in the number of species they had at that time.
However, experts believe that fast climatic change was already occurring far earlier in the Permian period, and that this occurred along with spikes in the diversity of reptiles. Researchers analysed fossils from 125 different species of reptiles to come to the conclusion that bursts of evolutionary diversity in reptiles were tightly correlated with relatively rapid fluctuations in climate throughout the Permian and for millions of years into the following geologic period, the Triassic. Their findings were published on August 19 in Science Advances.
According to Jessica Whiteside, a geologist at the University of Southampton in England who works on the topic of mass extinctions but was not involved in the new research, scientists are becoming more aware of the connection between evolution and changes in the environment, which is leading to an expansion of their understanding of evolution. This research will very certainly end up being a significant contributor to that discussion.
Tiago Simes, an evolutionary paleobiologist at Harvard University, and his colleagues took exact measurements and scanned fossils of reptiles ranging in age from 294 million to 237 million years old in order to explore the evolution of reptiles. In all, the researchers looked at 1,000 samples from 50 different research organisations located in 20 different nations. The scientists utilised an existing big database of sea surface temperatures based on oxygen isotope data, which dates back 450 million years and was released in 2021. This database was used to collect data on the climate.
The researchers discovered that the pace of climatic change was directly correlated with the rate at which reptiles developed. This was determined by meticulously monitoring the changes in body and head size and form that occurred in such a large number of species. The researchers determined that the greatest rapid pace of reptile diversification did not take place at the time of the end-Permian extinction, but rather several million years later in the Triassic, when climatic change was occurring at its most rapid rate and global temperatures were scaldingly high. According to Simes, the temperature of the ocean’s surface reached 40 degrees Celsius, which is equivalent to 1040 degrees Fahrenheit and is about equivalent to the temperature of a hot tub.
According to Simes, there have been a few species that have evolved more slowly than their relatives. What’s the big deal? Size. According to him, for instance, reptiles with lower body sizes are already preadapted to exist in areas that are fast warming up. “Small-bodied reptiles can better exchange heat with their surrounding environment,” and as a result, remain considerably cooler than bigger creatures. This is because small-bodied reptiles have a higher surface area to body ratio.
“At the same time, though, the natural selection was telling the huge reptiles, ‘You need to adapt right immediately or you’re going to become extinct.'”
According to Simes, this phenomena, which is known as the Lilliput effect, is not a novel hypothesis. He adds that it has been successfully shown in marine animals. However, this is the first time that it has been measured in vertebrates with limbs at this crucial time period in the history of the Earth.
The meticulous effort done by Simes and colleagues has helped to enhance the intricate evolutionary tree that depicts reptiles and their forebears. But for the time being, it is unknown whether factor had a more significant impact on the evolution of reptiles in the distant past: all of those open ecological niches after the end-Permian mass extinction, or the enormous temperature variations that occurred outside of the extinction event.
According to what Simes has to say, “We cannot tell which one was more crucial.” The progression of evolution throughout the Triassic period and the ascension of reptiles to worldwide domination in terrestrial ecosystems would have been very different if either one of these two factors had not been present.